Method of and apparatus for producing cap screws and the like



Nov. 22, 1927. 1,649,929

F. J. SENIOR 7 METHOD OF AND APPARATUS FOR PRODUCING CAP SCREWS AND THELIKE Filed Nov. 16, 1923 3 Sheets-Sheet l 3% F v & -;::.?.:?i;.:?; mummunnmn 4 5 j M1 .L 42

Patented Nov. 22, 1927.-

UNITED STATES PATENT OFFICE.

FREDERICK J". SENIOR, OF WATERBURY, CONNECTICUT, ASSIGNOR TO SCOVILLMANU- FACTURING COMPANY, OF NECTICUT.

METHOD OF AND APPARATUS FOR PRODUCING CAP SCREWS AND THE 'Lpplicatlonfiled November ered preferable to cutting because of its economy. Inthreading by die-rolling there must be some flow of metaleither radiallyor longitudinally of the blank. In the for mer case the metal flowsoutwardly to form the thread crests. Consequently the blanks arestepped; that is, the shank before threading has a smaller diameter thanthe shoulder. It is to this general mode of rolling threads that thepresent invention relates. The results of the attempts referred to,however, have not been altogether successful. For example, the screwsproduced have been objectionable to users because they do not resemblein appearance and do not havethe strength of a cap screw formed bycutting the thread. Another objection is found in the matter of formingthe shoulder. It is desirable to have the shoulder properly finished andaccurate in size. ,The shoulders of the blanks, as above stated, arelarger in diameter than the shanks because the metal of the shanks,during rolling, is displaced outwardly to form the crests of thethreads.

In carrying out the attempted methods referred to, when the blank ispassed between the threading dies the shoulder also is rolled forfinishing. It is difficult, however, to control the dimensions of theenlarged shoulder in forging the blank. Consequently, if the shoulder ofthe blank is undersize the shoulder after rolling remains undersize andlacks finish; if oversize, the tendency during rolling is to elongatethe blank or break the dies.

It is one of The present invention to provide an improved method of andapparatus for producing cap screws and the like, such that die-rollingmay be utilized for threading the blanks; such that the productapproximates, inapprincipal objects of the.

WATERBURY, CONNECTICUT, A CORPORATION OF CON- 16, 1923. Serial at.675,057.

pearance and strength, a cut thread product; and such that the shouldersof the screws produced are true ,to size and have a proper finish.

With this general object in view the invention consists in the method,articles, co'mbinations, details of construction, and arrangements ofparts which will first be described in connection with the accompanyindrawings and then more particularly pointed out.

In the drawings Figure 1 is a plan view, with parts in section,-of anapparatus constructed in accordance with the invention;

Figure-2 is an end view of the same;

Figure 3 is a perspective view (enlarged) of the two dies shown in Figs..1 and 2;

Figure 4 is an explanatory sectional view taken at right angles to thedie threads and through the blank and upper die of Fig. 3, when theblank is at the line H of Fig. 3, and the upper die is at acorresponding position;

Figures 5 and 6 are similar views taken when the blank is at the lines55, 6-6, respectively, in F i 3, and the upper die is moved according y;

Figure 7 is a s1m1lar view but showing both dies, when the blank is atthe line 7-7 of Fig. 3 and the upper die is moved accordingly;

Figure 8 is a of the dies;

. Figure 9 is a side view of a rough blank; Figure 10 is a similar viewof an intermediate blank;

Figure 11 is a similar view of the blank threaded but unfinished; and,

' Figure 12 is a similar view of the finished product.

Referring to the drawings, the desired product is a cap screw such asthat shown as an example, in Fig. 12. It has a head 21, a threaded shank22, and an unthreaded shoulder 23. The shoulder diameter isapproximately the outside or crest diameter of the threaded shank. Theshoulder has true diameter and is properly "finished, and the threadterminates regularly and definitely at the shoulder. In short, the screwas a whole approximates, in appearance and strength,

a cap screw formed by cutting.

top plan view of part of one the threads of which have been According tothe present invention, briefly stated, a blank is so formed and theblank is so threaded that the final turnof the thread adjacent to theshank has full crest diameter. Beyond the final turn of the thread themetal of the blank is upset in the form of a ridge or burr which, afterthreading, isremoved. And at some stage in the lines stated, thefinished product referred to,

may be formed from a rough blank such. as is shown, for example, in Fig.9. This blank has an unfinished round head 21, a shank 22*, and a roughfinished shoulder 23 which is somewhat oversize as to diameter andundersize as to length. Between the shank and shoulder is a bevel 24,hereinafter more fully referred to. This blank maybe formed in anysuitable manner, as byforging from shoulder may conveniently be donewhen theround stock in a heading machine. The head 21 is finished, as bymilling or diecutting, to form the desired head. Fig. 12 shows afillister head but the head may be polygonal, fiat or round, the headfinishing being a'well known operation and forming no part of thepresent invention. The shoulder 23 is machined, i. e. out, to true finaldiameter, thus giving it the desired finish and accuratesize. Thismachining of the head is machined to trim the top and bottom thereof. I

The above described operations provide what may be termed anintermediate blank, such as illustrated in Fig. 10. Thisintermediateblankhas a-finished head 21, a shank 22 and a shoulder 23which is finished to the final shoulder diameter but is somewhatundersize as to length. The total length of the intermediate blank isapproximately the length of the screw when finished. The difference indiameter between shoulder and shank equals the amount by Which'the metaloftheshank will be thrown outwardly in rolling the thread. 'Betweenshoulder and shank is a bevel 24". The angle of the bevel and thedeficiency in shoulder length are hereinafter referred to.,

The intermediate blank is die-rolled to thread the same, the threadingextending along the shank and part way up the bevel.

the extent being hereinafter more fully re- 7 ferred to. Thisdie-rolling operation is such as to upset the rolled metal into the formof a thread. The metal. of the blank is caused to flow outwardly to formthe thread crest, the outside diameter of which is approximately that ofthefinished shoulder. During the rolling operation described, only thatpart of the blank that is to be threaded is die-rolled, the shoulder andupper part of the bevel being left free. During threading, some of themetal of the bevel of the blank is caused to be upset and displacedoutwardly into the form of a ridge or burr beyond the final turn of thethread.

Fig. 11 illustrates this stage of the production. The uncompleted screwthere shown has a threaded shank 22 and an unthreaded shoulder 23.Beyond the final turn of the thread, adjacent the lower end of theshoulder is a ridge or burr 25 slightly great:

- er in diameter than the shoulder. The shoulder, for the most part,remains unchanged but there may be a slight enlargement of the lower endof the shoulder due to the crowding of the metal in forming the burr.Should this occur it is corrected when the burr is removed, as laterdescribed.

While the operations described may be 2 carried out by apparatus ofvarious construe tions, the invention in its entiret includes a suitableapparatus, one embo iment of which is illustrated in the drawings.Apparatusconstructed in accordance with the invention includes twocomplementary threading dies between which the blank rolls as -thethread is formed. As here shown as an example, slidable in upper andlower tracks 31, 32 of a bed block 33 is a slide 34 having a diecarrying portion 35. This latter carries a flat, substantiallyrectangular die block 36 which rests on a ledge 37 of the carrier 35 andis secured in place by means of clamps 38 and bolts 39. The outervertical face of the die block has a series of threading teeth 40hereinafter referred to. To reciprocate the die block 36, as here shownas an example, secured to the slide 34 is the end of a pitman 41 drivenfrom a 'rotary disk '42 by a crank pin 43 mounted shown. carried by theframeor bed'block is' an adjustably mounted supporting block 51. Theblock 51 has a ledge 52 on which is supported a die block 53 held inplace by clamps 54 and bolts 55 and arranged on a level with die block36 (Fig. 2). The outer vertical face of the die block 53 is formed witha series of parallel rectilinear teeth 56 running endwise of the blockbut at an angle to the longitudinal axis thereof (Fig. 8). The

teeth 40 of die 36 are similarly arranged, the teeth of one die,however, being opposed to the intervening grooves of the other die. Aswill be understood by those skilled in the art, the angle of the dieteeth with respect to the longitudinal axis of the die block, that is,with respect to the direction of travel of the blank, governs the leadof the thread formed. In carrying out the invention as here illustratedas an example, the die blocks 36, 53 are located substantially parallelandso spaced apart that the tooth crests are separated by a distanceless than, and the groove bottoms by a distance greater than thediameter of the shank of the blank.

That is, the groove bottoms, which determine the thread crest, arespaced apart a distance approximately equal to the diame ter of thedesired product. In the embodinient illustrated the position of dieblock 36 may be adjusted by the use of shims. Die block 53 is adjustedby adjustment of the supporting block 51 by means of bolts 57.

To facilitate the entrance of the blank between the dies, the opposingends of the dies are sloped or rounded off as appears in Figs. 1 and 3,giving, in effect, a bellmouth entrance for the blank.

In the apparatus here shown as an example, the ends of the teeth of thedies along the sides of the dies toward the blank head or what may betermed the trailing ends of the die teeth-are ground or chamfered ofiatan angle to the plane of the tops of the teeth Figs. 4-6). The angleof chamfer is later referred to. While one purpose of so constructingthe dies is to prevent the die teeth from chipping and breaking off atthe trailing ends during the threading operations, such a dieconstruction cooperates convenientlywith the bevel of the blank in theproduction of the desired product.

In carrying out the invention in its en tirety, the main portion of thethread is started prior to the final turns thereof. This may beaccomplished by die-rolling the blank between dies so formed that theteeth which roll the main portion of the thread have an initial positionin advance of the teeth which roll the final turns of the thread. Thedrawings illustrate dies adapted to accomplish this step. As illustratedin Fig. 8, the greater part of the die teeth of die 53 start at theforward end of-the block. At the side of the die-that is toward theblank head, .however, the final few teeth start progressivelyto therear, as shown in the lower right hand corner of Fig. 8. It will beunderstood that the die 36 is similarly formed. With the dies describedthe main part of the thread is well started before blank reaches theteeth that form the final turns of the thread.

- lVith the movable die drawn back to the end of its idle stroke (Fig.1), a blank is positioned adjacent the opposing ends of thecomplementary dies. To this end, there is provided means for fixing theposition of the blank with respect to the die teeth. That is, in termsof the embodiment illustrated, there is provided means for fixing thevertical position of the blank. As here shown as an example, the dieblock 36 extends beyond the line of termination of the chamfered dieteeth so that its top edge forms a ledge '60 for receiving the head of ablank. The die block 53 is similarly formed to provide a ledge 61. Theseledges receive the underside of the head of the blank which is vthussuspended between them. The ledges 60, 61 are spaced from the line oftermination of their respective die teeth a distance to cause the blankto be so positioned with respect to the die teeth that the desired pointon the blank comes opposite the line of termination of the teeth. Inother words, the blank should be so positioned thatthe shoulder and partof the bevel are beyond (above) the die teeth. As is known tothoseskilled in the art, there is a tendency for the blank to jump endwise inthe direction of its head when the teeth take hold. Consequently, unlessholddown devices are used, this jum must be allowed forin positioningthe b ank. The approximate amount of this jump, for a given set of dies,being known or readily ascertained, the ledges are spaced from the dieteeth accordingly. The ledges initially position the blank, which thenjumps, and thereafter the blank is held in the same relative axialposition by the inter-engagement of the die teeth and the formingthread.

Due to the extension of the die blocks 36, 53 to form the ledges 60, 61,the die blocks have plain surfaces 62, 63, that come opposite theshoulder and part of the bevel of the blank. lVhen'the die blocksare inplace, as here shown, the plain surfaces 62, 63 are spaced apart adistance substantially greater than the diameter of the shoulder 23 ofthe blank. Or, in terms of one die, its plain surface 62 (or 63) islocated in a plane not only below the teeth but below the plane of thebottom of the teeth (Fig. 2). Conse-' quently, when a blank is beingthreaded, the surfaces 62, 63 leave the shoulder of the blankentirelyfree and do not contact with the blank or any part thereof. Inother words, the surfaces 62, 63 play no part in the threading operationexcept in that the ledges 60, 61 position the blanks in feeding.-

A blank being suspended in position, as above described, the movin die36 is advanced and the blank is rolled between the two dies. That is,the blank revolves on its own axis and travels along between the dies asthe moving die advances. For a half turn of the blank the teeth of die36 form thread portions in half the surface of the 53 and the halfthread portions formed by (ill die 53 are presented to die36 for furtherformation or finishing or both, With the apparatus described, thecomplete thread is roughly formed during the first half turn or few halfturns of the blank, the remainder of the action being in the nature of afinishing or planishing operation. During this threading operation, thechamfered portions of the die teeth, acting on the bevel of the blank,thread part of the same and upset some of the metal into the form of aridge or burr beyond the final turn of the thread.

Fig. 4 shows the start of the operation and illustrates the relation ofblank and dies. It is to be understood that the moving die is drawn backfrom the position of Fig. 3 and has just started to the left as viewedin Figs. 1 and 3. The oncoming die teeth, because of the die blockformation, are indicated in dotted lines. This figure also shows therelation between the bevel of the blank and the chamfered die teeth.Fig. 5 illustrates the parts after the moving die has proressed farenough to form the thread. The die teeth have dug into the blank to formthe thread groove and. the metal has been displaced into the die groovesto form the thread crest. Fig. 5 also illustrates how the chamfered endsof the die teeth have threaded part of the bevel and have upset themetal into' a burr 25 beyond the final turn of the thread.

In the completion'of the desired product, the burr above referred to isremoved an the shoulder lengthened to final size. This may beaccomplished by working the upset metal into the shoulder to elongateit, the shoulder being carried down to a thread turn of full outsidediameter. For example, the partly finished blank may be subjected to arolling action which rolls the burr down to shoulder diameter, the metalthus displaced being received by the final turn of the thread.

This may be accomplished, for example, by apparatus including platens orplanishing dies, spaced apart a distance substantially equal to theshoulder diameter, and be tween which the blank is rolled. Oneembodiment of such an apparatus 'is shown in the drawings, theplanishing dies being incorporated as part of the die block unitsdescribed. As here shown, the corner of th. die 53 at the rear end andat the side toward the head of the blank (the lower left corner in Fig.8) is cut away to receive a platen or. planishing die block 70. Thisplaten is a substantially rectangular block having its longer axis inthe direction of the blank travel. Its outer side and end 00- incidewith the corresponding side and end ,of the die block 53 (Fig. 3). Itsblank-engaging surface is substantially parallel to the plane of thetops of the die teeth except that the forward end is slightly roundedoff to facilitate reception of the blank; The platen has a length suchthat it can act on the blank during several turns of the latter but suchthat it is not reached by the blank until the threading operation isfinished. The width of the platen is equal to the plain surface 63 plusseveral die teeth, or, in terms of the blank, it is wide enough to comeopposite the shoulder of the blank and several turns of the thread. Theplaten is so asso ciated with the die block 53 that its blank engagingsurface lies approximately in the plane of the bottom ofthe die teeth.

In the embodiment illustrated, the .platen is adjustably secured in thecutout recess in the'die block 53 by screws 71 passing through slots 72,and may be-adjusted by the use of shims. Cooperatin platen 70 is acomplementary .p aten 73 like platen 70 and similarly set in thecorrewith this sponding corner of die block 36. As the die 36 movesacross the die 53, andnear the end of the stroke, the platen (3 comesopposite platen 70 and part of the blank is rolled between them. As eachplaten has its planishing surface in the plane of the bottom of itsrespective die teeth, the two platens are separated a distancesubstantially equal to the diameter of the shoulder of the blank. Duringthe rolling operation the upset metal of burr 25 is rolled down by theplatens or 'planishing dies '70, 73, the displaced metal being receivedby the final turn of the (1 thread. That is, the metal is worked intothe shoulder to elongate it, carrying the' shoulder down to a threadturn of k full out-' side diameter. if the shoulder 23 of the partlycompleted blank was increased in diameter in the shoulder, which extendsdown toa thread turn of full outside diameter.

It is considered advisable to have the,

platens extend inwardly (downwardly) some distance beyond where the burris en countered. Theoretically the platen surfaces are tangential to thethread crest but It will now be apparent that the relation of the partsjust gradual step of such dimension that the dies will upset andrelations the product-ion of 1/ if it is found that the platens tend toflatten the thread crest, the platen surfaces may b}? ground off alongthe inner edges to avoid t is.

It will be noted thatwhile tlieblank is passing between the platens,partof the shank is still rolling between die teeth. At this stage,however, the thread has been completely formed and the die teeth havenofunction except, perhaps, to guide the blank.

As the moving die reaches the end of its rolling stroke the blankreaches the end of the stationary die and can drop out, to be collectedas esired. The moving die then makes an idle return stroke to initialposition, thus completing the cycle of operations for one blank. 1

Referring back tothe blank, it is noted that the bevel above mentionedneed not necessarily be a true bevel. That is, the surface may befrustro-conical or may be slightly rounded. What is desired is a down"from shoulder to shank such a burr as can be worked into theshoulder-to prolong the same as described. For convenience, however, theterm. bevel has been used. The angle of the bevel is not the same forall blanks. Generally speaking, the angle of bevel varies with thediameter of blank and'withthe depth of thread to be formed. As it isdifficult, even with these values known, to fix a standard, it isconsidered advisable to adopt a iven bevel and make a trial run. It haseen foun that for screws varying in diameter from 1/4" to 7/8" asuitable range of included bevel angles is from 20 to 30. This rangeprovides a starting point. fora given production run, correction beingmade, if necessary, after a trial run, As the difference in shoulder andshank diameter for a given size screw and given dies is fixed, thefixing of the bevel angle, of course, determines the axial length of thebevel.

The angle of chamfer of the die teeth the angle of varies, generallyspeaking, with the bevel. For the above mentioned ran e of screws, asuitable range of chamfer ang e gr is 25 to 35. As a starting point fora given run, the die blocks are conveniently formed so that the blank ispositioned in rolling to cause the threading to extend about two thirdsof the way up the bevel.

As an example, the following dimensions ave been found suitable forsteel cap screws, all figures being approximate: diameter of shank ofblank, 7 /16 diameter of shoulder after machining), 1/2; axial length ofvel, 5/32" (this gives an included bevel angle of about 24) length ofshoulder of blank, 28/6, varying slightly at different points around thecircumference of the blank;

as later described.

angle of chamfer of die .teeth, 30f; width of plain surfaces (62, 63)separating teeth from. sitioning ledges, 13/32" (this allows for a lankjump of about 1/8") diameter of shoulder and thread crest of screwproduced, 1/2; length of shoulder'of screw produced 1/2" incircumference- While the shoulder of a given standard size should havethe standard length at all points, a slight overlength immaterial.Variation, such as that above mentioned from a given shoulder length toa slight overlength is also found in cut thread products.

As unknown variables, such, for example, as the nature and condition ofthe stock used, may cause a slight deviation in results, it may benecessary to make a readjustment following a trial run. This may bedone, for example, by changing the anglenofv the bevel of the blank andof the chamfer of the dies, if they are chamfered. Or it may beaccomplished by a variation in the axial position of the blank withrespect to the die teeth. Thatis, if the bevel of the blank is to 33/64at opposite point at some points is die, there is not enough of a burrformed.

This may be corrected by new dies, new blanks, or by grinding down theledges of d the dies (60, 61) so as to so position the blanks that thethreading extends further up the bevel, more metal thus being upset intothe burr.

To review the operations described: From the rough blank of Fig-9, anintermediate blank as shown in Fig. 10 is formed, having a shoulder 2 3finished as to diameter but short as to length. With the movable die 36drawn back, a blank is suspended by its head from ledges 60, 61. Uponthe advance of die 36 the blank is rolled bet-ween the two dies, theteeth ofwhich upset the metal into the form of a thread, the metal beingdisplaced ooves to give a thread crest diameter equal to the shoulderdiameter. During the threading the die teeth upset some of the metal ofthe blank into the form of a burr, beyond the final turn of the thread.Near the end of the stroke of the moving'die the upper end of the blankis rolled between the platens or planishing dies 7 73. These roll downthe burr to shoulder diameter, working the metal into the shoulder toelongate it which carries the shoulder down to a threadorest outwardlyinto the die of full outside diameter and to the desired same timeproducing a cap screw the thread of which terminates regularly anddefinitely at the shoulder so that the screw has the appearance andstrength of a cut-thread product. Further, the shoulder is properlyfinished and is true to size.

What I claim is: v

1. The herein described method .of pro-' ducing cap screws and the likewhich comprises forming a blank having a shoulder and a shank smaller indiameter than the shoulder, and having a bevel between shoulder andshank, die-rolling the shank and part of the bevel to thread the same,the metal flowing outwardly to form the thread crest, causing part ofthe metal adjacent the end of the shoulder to be upset in the form of aridge or burr beyond the final turn of the thread, and removingsaidburr.

2. The herein described method of producing cap screws and the like,which com prises forming a blank having a shoulder and a shank smallerin diameter than the shoulder, and having a bevel between shoulder andshank, die-rolling the shank and part of the bevel to thread the same,the metal flowing outwardly to form the thread crest, causing part ofthe metal adjacent the end of the shoulder to be upset in the form of aridge or burr beyond the final turn of the thread, and rolling down saidburr to shoulder diameter. a X

3. The herein described method of producing cap screws and the like,which comprises forming a blank having a shoulder and a shank smaller indiameter than the shoulder, the shoulder being shorter than the desiredshoulder, and having a bevel between shoulder and shank, die-rolling theshank and part of the bevel to thread the same, the metal flowingoutwardly to form the thread crest, causing part of the metal adjacentthe end of the shoulder to be upset in the form of a ridge or burrbeyond the final turn of the thread, and working-the upset metal intothe shoulder to elongate it.

4:. The herein described method of producing cap screws and the like,which comprises forming a blank having a shoulder and a shank smaller indiameter than the shoulder, the shoulder being shorter than the desiredshoulder,-and having a bevel between shoulder and shank, die-rolling theshank and part of the bevel to thread the same. the, metal flowingoutwardly to form the thread crest, causing part of the metal adjacentthe end of 'the shoulder to be upset in the form of a ridge or burrbeyond the final turn of the thread, working the upset metal into theshoulder to elongate it, and at some stage in the production, machiningthe shoulder to desired diameter.

5. The herein described method of producing cap screws and the like,which comprises forming a blank having a shoulder and a shank smaller indiameter than the shoulder, and having a bevel between ShOlll'. der andshank, machining the shoulder to size, die-rolling the shank andpart ofthe bevel to thread the same, the metal flowing outwardly to form thethread crest, causing part of the metal adjacent the end of the I tweenshoulder and shank, machining the shoulder to size, die-rolling theshank and part of the bevel to thread the same, the metal flowingoutwardly to form thethread crest, causin part of the metal adjacent theend of the s oulder to be upset in the form of a ridge or burr beyondthe final turn of the thread, and working the upset metal into theshoulder to elongate it.

7. The herein described method of producing cap screws and the like,which comprises forming a blank having a shoulder and a shank smaller indiameterthan the shoulder, the shoulder being shorter than the desiredshoulder, die-rolling the shank to thread the same, upsetting some ofthe metal beyond the final turn of the thread, and working said upsetmetal to form an elongation of the shoulder.

8. The herein described method of prdducing cap screws and the like,which comprises forming a. blank having a shoulder and a shank smallerin diameter than the shoulder, die-rolling the shank to thread the same,causing the metal of the blank adjacent the end of the shoulder to beupset in the form of a burr or ridge, and finishing the shoulder toremove the burr.

9. The-herein described method; of producing cap screws and thelikeQwhich com prises forming a blank having a. shoulder and a shank ofsmaller diameter than the shoulder, the shoulder being of a lengthshorter than the length desired, machining the shoulder to size,threading the shank, and causing the shoulder to be given its desiredlength following the threading.

-10. In the method, herein described, of producing cap screws and thelike, the steps which consist in upsetting, during threading,

the metal of the blank into the form of a 1 ridge or burr be end thefinal turn of the and a shank smaller in diameter than the shoulder,cutting the shoulder to desired.

ed method of PI'Q'.

beyond the final turn diameter, and die-rolling the shank to thread thesame.

12. The herein described method of producingcap screws and the like,which comprises forming a blank having a shoulder and ashank smaller indiameter than the shoulder and having a bevel between shoulder andshank, and die-rolling the blank to thread the shank and part of thebevel, the shoulder and upper part of the bevel being left free during.the threading operation.

13. In apparatus of the class described, and in combination, means forthreading a cap screw blank and causing, during threading, the formationof a burr on the blank beyond the final turn of the thread, and meansfor removing the burr.

14. In apparatus of the class described,

and in combination, means for threading a cap screw blank and causing,during threading, the formation of a burr on the blank of the thread,and means for rolling down the burr to the diameter of the shoulder ofth'eblank.

15. In apparatus of the class described, and in combination, means forthreading a cap screw blank and causing, during threading, the formationof a burr on the blank beyond the final turn of the thread, and meansfor working the metal of the burr into the shoulder of the blank toelongate the shoulder.

16. In apparatus of the class described,

and in combination, two complementary threading dies for threading a capscrew blank and. causing, during threading, the formation of a burr onthe final turn of the thread, two complementary planishing dies forrolling down said burr and working the metal into the shoulder of theblankto elongate the shoulder, and means for causing relative movementof the threading dies and the planishing dies.-

17. In apparatus of the class described, and in combination, twocomplementary threading dies for threading a cap screw blank, means forpositioning the blank to leave the shoulder of the blank free of thedies during threading, thereby to permit the dies to cause a burr to beformed beyond the final turn of the thread, and two complementaryplanishing dies for rolling down said burr and working the metal intothe shoulder of the blank to elongate the shoulder.

18. In apparatus of the class described, and in combination, twocomplementary threading dies for threading a cap screw blank, to leavethe shoulder of the blank free of the dies during threading, thereby topermit the dies to cause a burr to be formed beyond the final turn ofthe thread.

19. In apparatus of the class described,

the blank beyond,

and means for positioning theblank die comprising a block a ledgeparallel to the line of termination of the chamfered teeth forpositioning a blank, the surface of the block between said ledge and theteeth being in a plane below the plane of the bottoms of the die teeth.

21. In combination, a threading die comprising a block having a seriesof parallel oblique teeth the trailing ends of which are chamfered and aledge parallel to the line of termination of the chamfered teeth forpositioning a blank, the surface of the block between said ledge and theteeth being in a plane below the plane of the bottoms of the die teeth,and a planishing die having its planishing surface substantially in theplane of the bottoms of the die teeth.

22. In combination, a threading die comprising a block having a seriesof parallel oblique teeth the trailing ends of which are chamfered and aledge parallel to the line of termination of the chamfered teeth forpositioning a blank, the surface of the block between said ledge and theteeth being in a plane below the plane of the bottoms of the die teeth,the block being cut away to form a recess adjacent the rear end thereofin line with said surface but wider than the latter, and a planishingdie located in said recess and having its planishing surfacesubstantially in the plane of the bottoms of the die teeth.

23. In combination, a threading die comprising a substantiallyrectangular block having a series of parallel teeth, and a planishingdie associated with said block adjacent one rear corner, the width ofsaid planishing die being such as to extend both outwardly and inwardlybeyond the line of termination of the die teeth, and its planishmg ofthe'bottoms of the die teeth.

24. In apparatus of the class described, and in combination, twocomplementary threading dies for threading a cap screw blank, means forpositioning a blank so that its shoulder is beyond the die teeth to befree of the dies, and two complementary planishing dies spaced apart adistance substantially equal to the distance between the planes of thebottoms of the die teeth and said dies having 0 parallel obliqueteeththe associated with the threading dies to act line of terminationof the teeth and the on the shoulder of the blank after the blank edgeof the block, which lies in a plane behas been threaded. v low the planeof the bottom'of said teeth. 10

25. A thread rolling die comprising a In testimony whereof, I havehereunto block having a series of parallel teeth which set my hand.

terminate short of one of the edges of the block, and having a surface,between the FREDERICK J. SENIOR.

